Fig. 3

Origin of the mitochondrial linear plasmids in seed plants. A Annotated protein domain architectures of complete mitochondrial linear plasmids from fungi. B Annotated protein domain architectures of complete mitochondrial linear plasmids from plants. Protein domains shared by fungal and plant mitochondrial linear plasmids are labeled in dark blue. Fungal and plant specific protein domains are labeled in beige and pink, respectively. Charts indicate the occurrence frequency of different protein domains in the corresponding groups. The circle size is proportional to the occurrence frequency of protein domains. Numbers near the circles represent domain names (important domains are specified) and are consistent with the numbers near the protein domain names in the charts. The thickness of lines linking two circles is proportional to the frequency at which the two protein domains appear in a complete element. C Venn diagram of annotated protein domains in fungal and plant mitochondrial linear plasmids. Protein domains shared by fungal and plant mitochondrial linear plasmids are highlighted in dark blue. Fungal and plant specific protein domains are highlighted in beige and pink, respectively. D Genome maps of representative Polin-MEs, fungal mitochondrial linear plasmids and plant mitochondrial linear plasmids. E Hypothetical scenarios for the origins and evolution of plant mitochondrial linear plasmids